Until now, vapor-liquid mixtures exiting from mixed-phase fixed bed catalytic reactors have been separated into separate vapor and liquid phases by means of vertically or horizontally-disposed separator drums separate to and installed downstream of the reactors. The vapor-liquid mixtures are normally transported at relatively high velocities, for example, 20 to 50 ft./sec., from the reactor to the separator drums, where separation is effected.
The effectiveness of a vapor-liquid separator depends on the minimum droplet size that can be separated in the device and the quantity of material in the mixture to be separated is in the form of droplets smaller than this minimum droplet size. Accordingly, it will be appreciated that the larger the droplet size in the mixture to be separated, and the smaller the quantity of material in the mixture in the form of droplets smaller than the minimum droplet size that can be separated, the more effective the separation. Moreover, the drop size distribution of a vapor-liquid mixture is critically dependent on its previous history. For example, when such a mixture is transported under high velocities, it is subjected to high shear stresses with the results that a greater proportion of small droplets form than if it were transported at relatively low velocities. Notwithstanding the above, where the conventional separation drums are employed downstream of the fixed bed reactors, the mixtures to be separated are transported under the relatively high velocities of 20 to 50 ft./sec. in order to reduce the size and cost of the transfer line, even though separation effectiveness is somewhat sacrificed.